Design and Synthesis of Calixarene‐Based Bis‐alkynyl‐Bridged Dinuclear AuI Isonitrile Complexes as Luminescent Ion Probes by the Modulation of Au⋅⋅⋅Au Interactions

Two calixarene-based bis-alkynyl-bridged Au (I) isonitrile complexes with two different crown ether pendants, calix[4arene- (OCH (2) CONH-C (6) H (4) Ctriple bondC) (2) Au (CNR) (2) ] (R=benzo15crown-5 (1) ; R=benzo18crown-6 (2) ), together with their related crown-free analogue 3 (R=C (6) H (3) (OMe) (2) -3, 4) and a mononuclear gold (I) complex 4 with benzo15crown-5 pendant, have been designed and synthesized, and their photophysical properties have been studied. The X-ray structure of the ligand, calix4arene- (OCH (2) CONH-C (6) H (4) Ctriple bondCH) (2) has been determined. The cation-binding properties of these complexes with various metal ions have been studied using UV/Vis, emission, (1) H NMR, and ESI-MS techniques, and DFT calculations. A new low-energy emission band associated with AuAu interaction could be switched on upon formation of the metal ion-bound adduct in a sandwich fashion.